Mosquito problem, need help

I have a water trough in my backyard that deer and so on drink out of. I have a cat that lives on my back porch that also drinks out of it, despite the fact that I put water out for it in a bowl. You know how cats are. Problem is, it's full of mosquitos, and those same mosquitos are all over my back porch and yard. I thought I had found some tablets you can put in the water that will kill them. When I read the label on the package it said it was harmful to humans. If it's harmful to humans I assume it is for animals as well. Is there anything that I can put in it to kill them off? That won't also kill the deer and cats that drink out of it?

Mosquito problem, need help

I found something that looked like that at Lowes. Mosquito dunks if i remember correctly. It said on the box to wash your hands and all that after using it, call poison control if you ingest it, and so on. I was worried that if it's poisonous for humans, wouldn't it kill pets to?